First-episode psychosis and autism spectrum disorder: a scoping review and a guide to overcome diagnostic challenges

Background: Undiagnosed Autism Spectrum Disorder (ASD) may represent a diagnostic challenge in people who refer to specialized services for first-episode psychosis (FEP). Similarly, individuals with ASD can present newly-onset psychotic symptoms. Aims: The present review aimed to summarize the literature available on ASD and FEP to guide differential diagnosis between the two conditions and discuss the impact of ASD-FEP comorbidity on recovery. Methods: The PRISMA-ScR guidelines were followed. After conducting a comprehensive literature search, we screened 204 papers including participants with: (1) a comorbid diagnosis of FEP and ASD; (2) FEP and autistic traits; (3) separate groups of FEP and ASD. Results: A total of 18 studies were discussed and confirmed the high prevalence of ASD or autistic traits in people referring to FEP services (up to 9% and 35% of FEP, respectively), which could negatively impact pathways to care, clinical presentation, and outcomes. Due to some similarities in ASD and FEP presentation (e.g., difficulties in social functioning), a differential diagnosis could be challenging. The features more suggestive of ASD rather than a primary FEP include illogical and concrete thinking, and a longstanding social interaction difficulty. Aberrant salience and suspiciousness can manifest in ASD, but are usually more transient, and stress-related than in FEP. Also, perceptual abnormalities are due to altered sensory processing rather than pathological hallucinations. The co-occurrence of ASD symptoms is associated with a reduced probability of clinical and functional recovery in FEP, a higher risk of suicidal behaviors, and higher unemployment rates. Conclusions: The kaleidoscopic manifestations of FEP require an adequate differential diagnosis that should include ASD. FEP services ought to be equipped for an adequate assessment and diagnostic formulation, which can result particularly challenging should symptoms of autism be present in adult patients.